Planting trees is one of the most effective activities in recovering soil organic carbon (SOC) stocks of degraded areas, but we still lack information on how different tree species can influence soil respiration, one of the main sources of dioxide carbon (CO2) to the atmosphere. This study aimed to explore the influence of different forest species on the autotrophic and heterotrophic components of the total soil respiration in a bauxite mining area under reclamation. We analysed the soil CO2 efflux under five treatments: i) monoculture of clonal Eucalyptus; ii) monoculture of Anadenanthera peregrina (L.); iii) a mixed plantation of 16 native forest species (Nat); iv) a mined area without vegetation cover; and v) a natural forest cover. This design allowed exploring the soil CO2 dynamics in a gradient of recovery, from a degraded area to natural vegetation. Additionally, we measured soil temperature, moisture and soil characteristics. Soil CO2 efflux increased with increasing forest species cover in the rainy months. There was no significant change in CO2 efflux among the tree species. Heterotrophic soil respiration contributed to 64% of total soil CO2 efflux and was associated with litter decomposition. Amongst the abiotic variables, increases in soil moisture had the most influence on CO2 efflux. Therefore, these results help to understand the factors that underpin the loss of SOC and can orient management practices to improve soil organic matter and restore soil quality in degraded areas.

Forest cover can be effective in reducing the changes caused by mining, especially through the recovery of organic matter stocks. The objective was to evaluate the C and N stocks in fractions of soil organic matter in bauxite-mined area under rehabilitation with forest species. The forest covers evaluated were: eucalyptus (Euc), A. peregrina (Ap) and a mixed planting of native forest species (Nat), in addition to an area without forest cover (WCov) and native forest in an unmined area (NV). The fertilization treatments studied were a standard adopted by the company (SF), organic fertilizer (OF), chemical fertilizer (CF) and OF + CF. The total stocks of C and N from particulate organic matter (POM), mineral-associated organic matter (MOM), microbial biomass (MB) and labile C (LC) were estimated, as well as the C/N ratio and the carbon management index (CMI). The influence of the presence or absence of litter was evaluated, as well as the roots on C and N stocks in the soil. The stocks of total and labile C, CMI and MBC did not differ between the forest covers studied in the 0-60 cm layer, being lower than those in NV and higher than those found in WCov. The other variables (TN, CMOM, NMOM, CPOM, NPOM and MBN) were higher only in the NV. Mining causes reduction of organic matter fractions; however, forest cover increase the stocks of TOC, LC and CMI. Roots are more associated with the recovery of C and N stocks than litter and trunk biomass.